BOSTON — People with lower percentages of body fat are not necessarily at lower risk for diabetes and heart disease, according to a new international study.

The study identified a gene that is linked with having less body fat but also with having an increased risk of Type 2 diabetes and heart disease. The investigators examined the genomes of more than 75,000 people and found that the gene, IRS1, was linked to less body fat, but also to unhealthy levels of cholesterol and blood glucose.

“We’ve uncovered a truly fascinating genetic story. ... When we found the effect of this gene, we were very intrigued by the unexpected finding,” said study researcher Douglas Kiel, a professor at the Harvard Medical School and researcher at the Institute for Aging Research at HMS affiliate Hebrew SeniorLife. “People, particularly men, with a specific form of the gene are both more likely to have lower percent body fat [and] to develop heart disease and Type 2 diabetes. In simple terms, it is not only overweight individuals who can be predisposed for these metabolic diseases.”